This invention relates to the suspension of a rear axle gear casing for motor vehicles wherein driving forces are transmitted from the cardan shaft and the drive shaft to the rear axle shafts via the rear axle gear casing.
Rear axle gears of motor vehicles which, in a conventional way, are driven by means of a cardan shaft extending in the driving direction and transmitting the drive to the wheels by means of transversely extending axle shafts, are subject to moments of reaction during the driving which are effective around the axes of the cardan shaft (cardan shaft moment) and also around the transversely located axis of the axle shafts (starting moment). In this case, the reaction moments, corresponding to the gear reduction provided in the axle gear casing, are at a certain proportion to one another and must be absorbed in the suspension points of the axle gear casing at the vehicle body.
In the case of an elastic suspension of the rear axle gear casing, the mentioned reaction moments cause movements of the axle gear casing around the axis defined by the resulting momental vector. These movements are especially present when the elastic suspension elements have a high coefficient of elasticity, which is desirable for the purpose of noise reduction.
Such movements result in a change of the angle between the axis of the drive shaft of the rear axle gear and the axis of the cardan shaft driving it. This angle change causes additional stress which reduces the durability of a flexible disk that is conventionally inserted between the cardan shaft and the gear drive shaft. The angle change also increases the inbalance in the momental transmission, in addition to noise and vibrations.
A known suspension for a rear axle gear casing of the above-mentioned type is shown and described in German Unexamined Published Application (DE-OS) No. 15 30 516. In the case of this construction, the front and the rear suspension elements of the gear casing are staggered with respect to the longitudinal central axis of the gear in such a way that a straight line connecting these elements with one another is perpendicular to the resulting momental vector and is thus located in the momental support plate. The resulting forces can therefore all be absorbed in the suspension points.
In the case of the above-mentioned German Unexamined Published Application (DE-OS) No. 15 30 516, the elastic suspension elements are stressed by tension or pressure by the resulting driving forces with the result that the gear casing, corresponding to the elasticities existing in the suspension elements, can swivel around an axis that is defined by the resulting momental vector. As a result, angle changes occur between the drive shaft and the carban shaft, which changes may exceed the permissible extent, especially when a high coefficient of elasticity is chosen for the suspension elements during peak loads.
The present invention is therefore based on the objective of providing a suspension for axle gear casings which, in the case of a sufficiently high elasticity of the suspension elements, can absorb starting and cardan shaft moments without the occurrence of undesirably large changes of the angle between the drive shaft and the cardan shaft.
The particular predetermined configuration of the suspension elements achieves this objective.
The development according to the invention has the result that in the case of the occurring loads, swivel movements of the axle gear casing come together in space, such that the superimposing movements that result from the cardan shaft moment and the starting moment overlap in opposite directions. The resulting compensation has the effect that relatively soft suspension elements may be used without causing unacceptably large changes of the angle between the drive shaft and the cardan shaft.
Preferred embodiments of the invention include a suspension system wherein at least one of the suspension elements is located behind the rear axle shaft. Other preferred embodiments include a suspension system having two suspension elements that are aligned with one another in the longitudinal direction of the vehicle. These configurations are advantageous in regard to the arrangement of the axle gear casing relative to the vehicle body.
Other preferred embodiments of the invention include a suspension system wherein both suspension elements are subject exclusively to a load in the radial direction.
The above characteristic is advantageous in that the suspension elements may be arranged identically with respect to the longitudinal central axis of the axle gear casing, and further, be designed identically.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawings(s) which show, for purposes of illustration only, an embodiment 1 several embodiments in accordance with the present invention.